[VL][MINOR] Allow build_gluten_cpp read custom velox home #313

Job	Run time
build-native-lib-centos-7	1s
run-cpp-test-udf-test	1h 39m 8s
run-tpc-test-centos	0s
run-tpc-test-ubuntu	0s
run-tpc-test-ubuntu-iothreads	0s
run-tpc-test-ubuntu-oom	0s
run-spark-test-spark32	0s
run-tpc-test-centos8-uniffle	0s
run-tpc-test-ubuntu-2204-celeborn	0s
run-tpc-test-ubuntu-randomkill	0s
run-spark-test-spark32-slow	0s
run-spark-test-spark33	0s
run-spark-test-spark33-slow	0s
run-spark-test-spark34	0s
run-spark-test-spark34-slow	0s
run-spark-test-spark35	0s
run-spark-test-spark35-scala213	0s
run-spark-test-spark35-slow	0s
	1h 39m 9s

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